Leave boxer with European football player (6)
I believe the answer is:
'football player' is the definition.
(I've seen this before)
'leave boxer with european' is the wordplay.
'leave' becomes 'go' (to go is to depart or leave).
'boxer' becomes 'ali' (Muhammad Ali).
'with' means one lot of letters go next to another.
'european' becomes 'E' (abbreviation e.g. EU).
(Other definitions for goalie that I've seen before include "Footballer" , "Hart perhaps" , "number one" , "one saves" , "Football team member" .)